3D MR imaging with fat suppression

Abstract

In a method for image generation by magnetic resonance with suppression of a spectral component of the magnetic resonance signal during the signal acquisition, k-space is sampled in sub-sections, an excitation pulse for excitation of the spectral component to be suppressed is radiated at a point in time TI before acquisition of each sub-section of k-space, and different TI values are selected for the respective sub-sections.

1. A method for generating a magnetic resonance data set from which an image of an examination subject can be produced, comprising the steps of:
 exposing an examination subject to a magnetic resonance data acquisition pulse sequence including acquiring a magnetic resonance signal from the examination subject, said magnetic resonance signal comprising multiple signal components and representing raw magnetic resonance data and, in said pulse sequence, activating an excitation pulse for excitation of a selected spectral component to be suppressed; 
 dividing k-space into a plurality of sub-sections and entering said raw data into k-space respectively in said sub-sections; 
 in said pulse sequence, activating said excitation pulse for said selected spectral component at a point in time T 1  before entering said raw data into each of said sub-sections of k-space, with T 1  being different for the respective sub-sections; and 
 making k-space, in which said raw magnetic resonance data has been entered, available in a form suitable for generating a magnetic resonance image of the examination subject therefrom. 
 
   
   
     2. A method as claimed in  claim 1  wherein k-space comprises a center region, and comprising dividing k-space into said sub-sections to cause respective portions of said center region to be contained in respectively different sub-sections, so that said raw data are entered into the respective portions of said center region for respective sub-sections associated with different points in time T 1 . 
   
   
     3. A method as claimed in  claim 1  comprising selecting the respective points in time T 1  for the respective sub-sections to produce a distribution of points in time T 1  around an average value that is selected dependent on parameters associated with said pulse sequence. 
   
   
     4. A method as claimed in  claim 1  comprising entering said raw data into the respective sub-sections of k-space along a trajectory proceeding radially outwardly from a center of k-space. 
   
   
     5. A method as claimed in  claim 1  wherein k-space has a center, and wherein the step of dividing k-space into a plurality of sub-sections comprises dividing k-space into a plurality of segments of a circle, each segment including said k-space center. 
   
   
     6. A method as claimed in  claim 1  comprising, in said pulse sequence, reading out said magnetic resonance signal with a three-dimensional gradient echo sequence. 
   
   
     7. A method as claimed in  claim 6  wherein said three-dimensional radiant echo sequence comprises two phase coding directions, and comprising entering said raw data into k-space radially in each of said phase coding directions. 
   
   
     8. A method as claimed in  claim 1  comprising exposing said examination subject to a static basic magnetic field of greater than 1.5 T tesla while exposing said examination subject to said pulse sequence. 
   
   
     9. A method as claimed in  claim 1  wherein said magnetic resonance signal comprises a fat signal component, and selecting said fat signal component as said signal component to be suppressed. 
   
   
     10. A method as claimed in  claim 1  comprising maintaining constant a time between entering said raw data into successive ones of said sub-sections of k-space. 
   
   
     11. A method as claimed in  claim 1  comprising changing said point in time T 1  linearly for the respective sub-sections of k-space. 
   
   
     12. A method as claimed in  claim 1  comprising exciting said magnetic resonance signal in said examination subject by irradiating the examination subject with a radio frequency field having a field distribution associated therewith, and comprising varying said points in time T 1  to produce a distribution of points in time T 1  around an average value that is selected dependent on said field distribution. 
   
   
     13. A method as claimed in  claim 1  wherein k-space has a center region and comprising dividing k-space into said plurality of sub-sections so that each of said sub-sections contains a portion of said center region, and entering said raw data into the respective portions of said center region in the respective sub-sections at said respective points in time T 1 , and entering raw data into other portions of each sub-section before and after the point in time T 1  associated with that respective sub-section.